Aqueous developable color proofing elements

ABSTRACT

Water coatable and water developable negative-acting color proofing single sheet and overlay systems are described. The water-soluble photosensitive color layer employed in each type of proofing construction includes a photopolymerizable polymer having a weight-average molecular weight between 5,000 and 100,000; an alkaline soluble resin having a weight-average molecular weight between 1,000 and 200,000 and an acid number between 50 and 300; and a water-soluble photoinitiator.

FIELD OF THE INVENTION

This invention relates to aqueous developable pre-sensitized colorproofing elements. In particular, this invention relates tonegative-acting overlay and single sheet color proofing elements thatare manufactured using aqueous coating compositions and developed withan aqueous developer, thus providing an environmentally friendly colorproofing system.

BACKGROUND

In color reproduction, the color accuracy of graphic art colorseparation negatives are generally verified using color proofing systemsprior to making the corresponding printing plates. The color proofingsystems must provide a consistent representation of the final colorprint. It is well known in the art that the halftone dot retention playsa significant role in the color rendition of the final image. Slightchanges in the dot reproduction curve can cause significant changes invisual color perception.

Several different types of color proofing systems are well known in theliterature. Both digital and conventional proofing systems are availablecommercially. In digital systems, digitized data is used to directlyimage the color proofing materials. However, conventional proofingsystems are primarily used when verifying the color accuracy of graphicart color separation films. Conventional color proofing systems consistof two types: overlay and surprint. Overlay systems provide a convenientand quick way to visualize a representative color on a transparentsubstrate. A typical overlay film construction includes a polyestersubstrate and photosensitive color layer. Optional protective layers mayalso be included over the surface of the photosensitive color layer. Acolor proof is constructed by individually imaging and developing eachrepresentative color proofing film. The color imaged films are then laidupon each other in register on a paper stock, thus providing a quick andsimple color proof composite. Examples of these types of constructionsmay be generally found in U.S. Pat. Nos. 3,136,637; 4,304,836;4,482,625; 4,634,652; 4,748,101; 4,952,482; and 5,258,261.

A surprint proof is generated by successively superimposing differentcolored layers upon each other on a single sheet. The surprint colorproofing materials are composed of two primary types: photosensitiveprecolored sheets and photosensitive colorless sheets whose latent imagemay be toned with pigments, inks or dyes. Some examples of post-coloredproofing materials may be found in U.S. Pat. Nos. 3,060,024; 3,634,087;and DE 3,336,431.

An example of one type of precolored proofing system includesphotosensitive constructions that are imaged prior to lamination to thereceptor or intermediate sheet. Representative examples of these typesof systems are described in U.S. Pat. Nos. 4,482,625 and 4,304,836.

Another type of precolored proofing system includes photosensitiveconstructions that are imaged and developed after lamination to areceptor or intermediate sheet. For example, U.S. Pat. No. 3,671,236describes a negative acting presensitized color proofing elementcomprising a carrier sheet having a smooth release surface, a diazosensitized color layer and a non-photoactive barrier layer upon whichmay be coated a pressure sensitive adhesive or a thermal adhesive asdescribed in U.S. Pat. No. 4,656,114. The developing media for thissystem is a 50:50 mixture of n-propanol and water. The barrier layer ispresent as a carrier for the image and to reduce interaction between theadhesive and the photoactive layer. U.S. Pat. Nos. 4,650,738; 4,751,166;4,808,508; 4,929,532; and 5,008,174; EP 365,356 and EP 365,357 patentapplications describe improvements on this construction by eliminatingthe need for a barrier layer between the diazo based photoactive layerand the adhesive. The developer used in these systems are aqueous alkalisolutions containing greater than 3% surfactant.

U.S. Pat. No. 4,596,757 discloses a further improvement on theconstruction described in U.S. Pat. No. 3,671,236 by utilizing a photomonomer system in place of the diazonium binders. Again an aqueousalkali developer is used which contains high concentrations of asurfactant (the example cited used 8.5%).

U.S. Pat. No. 5,248,583 describes a construction which utilizes aphotoactive color layer containing a photo-oligomer as thephotopolymerizable component and a photopolymerizable barrier layer toprovide a proofing element that can be developed in a low solids aqueousdeveloper having a pH of 10.2. This construction allows one to developthe image using a more environmentally compatible effluent since theaqueous developer contains less caustic and less ingredients than thoseused in the previously described systems.

To achieve a system that is developable in a developing solution havinga more neutral pH, the binders used in the photosensitive proofingformulation typically make the image more susceptible to attack by thedeveloper. When the resistively developable image is swelled or attackedby the developer it becomes increasingly more difficult to hold thehighlight dots (0.5-10% halftone dots) without sacrificing the shadowareas (90-99.5% halftone dots). The shadow areas are sacrificed when thephotosensitive layer is overexposed to achieve sufficient cross-linkdensity in the highlight dots to resist developer attack. However, whena photosensitive layer is overexposed, the shadow areas begin to fill-indue to halation effects. This over-exposure also increases the overalldot gain, which significantly affects the color rendition. Therefore,there exists a need for a proofing system that maintains highlighthalftone dots without over-exposure and is developable in an aqueousdeveloper having low solids and a pH less than 10.5.

Some attempts have been made to provide proofing elements that arecoated out of water and developed with water. For example, U.S. Pat. No.5,443,937 describes a photosensitive element based a photosensitivepolymeric diazo resin. However, polymeric diazo resins typicallygenerate color upon exposure to light which effects the final color ofthe image. In the printing industry, the color rendition of the proof isa critical factor of the proofing system. Any changes must becompensated for in the initial formulation of the color coatings.Adjustments to the formulations are a tedious task since the compositionhas to be coated, dried and exposed before an evaluation of the colorcan be performed. In addition, negative images using diazonium resinsmust be post exposed to light to stabilize the color. This post exposurestep adds an additional step to the proof making process. Therefore,there is still a need for a water coatable and water developable colorproofing element that does not have the disadvantages of color shiftsdue to the generation of color by the diazo resins and does not requireadditional process steps.

U.S. Pat. No. 4,041,204 describes a photosensitive sheet using a watercoatable and aqueous developable photosensitive color layer. Even thoughthe examples disclose the use of water to develop the image, the sheetis soaked in water for about a minute before spraying to complete theremoval of the unexposed areas. In other examples, the image wasdeveloped with a 4% solution of hydrogen peroxide. Resolution is notdiscussed and would not be a critical issue in stencil applications.

SUMMARY OF THE INVENTION

The present invention provides both a negative-acting photosensitiveoverlay color proofing element and a negative-acting photosensitivesingle sheet color proofing element. The photosensitive elements can bemanufactured using aqueous coating solutions and developed with aqueousdevelopers. In one embodiment of the present invention, an overlay colorproofing element is provided comprising a carrier having coated thereonin the following order: (a) a water-soluble photosensitive color layercomprising (i) an acrylated polymer (or oligomer) having at least onependant acrylate group and a weight-average molecular weight between5,000 and 100,000, (ii) an alkaline soluble resin having aweight-average molecular weight between 1,000 and 200,000 and an acidnumber between 50 and 300, (iii) a colorant or texturing material, and(iv) a photoinitiator; and (b) a water-soluble oxygen barrier layer.Preferred photoinitiators are water-soluble or water-dispersiblephotoinitiators having the following general structure: ##STR1## whereinX is chlorine or bromine; R¹ is selected from the group consisting ofhydrogen, trichloromethyl, tribromomethyl, aryl, and alkyl having up to15 carbon atoms; L is a linking group selected from the group consistingof carbamato, carbamido, amino, amido, alkyl having up to 15 carbonatoms, oxy, alkenyl, alkynyl, keto, ester, sulfonyl, aryl andcombinations thereof; and A is an acid group selected from the groupconsisting of carboxylic acid (--CO₂ H), sulfonic acid (--SO₃ H),phosphonic acid (--PO₃ H) and salts thereof. Both the photosensitivecolor layer and the oxygen barrier layer may be coated out of water. Inaddition, the color proofing element may be developed with an aqueousdeveloper having a pH between approximately 7.0 and 9.0 includingordinary tap water.

In another embodiment of the present invention, a negative-acting singlesheet color proofing element is provided comprising a carrier havingcoated thereon in the following order: (a) a water-soluble releaselayer; (b) a water-soluble photosensitive color layer comprising (i) anacrylated polymer (or oligomer) having at least one pendant acrylategroup and a weight-average molecular weight between 5,000 and 100,000,(ii) an alkaline soluble resin having a weight-average molecular weightbetween 1,000 and 200,000 and an acid number between 50 and 300, (iii) acolorant or texturing material, and (iv) a photoinitiator; (c) awater-soluble photopolymerizable inter-layer; and (d) a water-emulsionadhesive layer.

As used herein "water-soluble" or "water-dispersible" refers tomaterials that are soluble or dispersible in water and are capable ofbeing readily solublized or re-dispersed in an aqueous developer oncedried into a film or coating. For simplicity, the terms "water-soluble"and "water-dispersible" will be used interchangeably. "Water-emulsion"or "latex" refers to materials which are suspended in water, but becomeinsoluble in water once coalesced into a film or coating.

The term "texturing material" refers to materials that give the image atextured appearance. In other words, the materials give the image adimensional quality as opposed to a uniformly flat, smooth aspect. Forexample, the addition of silica gives a matte or deglossed appearance.

The term "acrylated", as used herein, includes not only pendant groupsbased on esters of acrylic acid, but also acrylamides, methacrylates andcrotonates.

DETAILED DESCRIPTION OF THE INVENTION

Water coatable and water developable negative-acting color proofingsingle sheet and overlay systems are described. The water-solublephotosensitive color layer employed in each type of proofingconstruction includes a photopolymerizable polymer having a molecularweight between 5,000 and 100,000; an alkaline soluble resin having amolecular weight between 1,000 and 200,000 and an acid number between 50and 300; and a water-soluble photoinitiator.

The overlay construction generally comprises a carrier having coatedthereon: (a) a water-soluble photosensitive color layer; and (b) awater-soluble oxygen barrier layer. When the imaged element is developedwith an aqueous developer, the unexposed areas of the photosensitivecoating are removed and the cross-linked image remains on the carrier.The imaged elements are then overlaid upon each other in register toform a composite multi-colored proof which may be mounted on anyreceptor.

Preferably, the carrier is a dimensionally and chemically stable plasticsheet, more preferably a 2.0 to 3.0 mil (5.1 to 7.6 cm) polyester film.To assist in the handling of the films, it may be desirable to includean antistatic coating, such as the antistatic coating comprising acolloidal silica crosslinked with an ambifunctional silane couplingagent described in U.S. Pat. No. 5,344,751. In addition, ananti-reflection coating(s), such as those described in U.S. Pat. Nos.4,340,276; 4,634,652; and 4,748,101, may also be included in theconstruction to reduce the interference patterns when viewing thecomposite proof.

The overlay construction includes an oxygen barrier layer applied overthe photosensitive color coating. Additives may be incorporated into theoxygen barrier layer to impart other desirable properties. For example,the oxygen barrier layer may contain particulates, such as polymericbeads or silica to assist in vacuum draw-down in the exposure frame andimprove handling properties, or anti-halation materials to improveresolution, or UV absorbers to balance exposure times of the variouscolors. The oxygen barrier layer must be capable of being removed duringdevelopment of the image. Preferred oxygen barrier layers include watersoluble resins, such as alkyl ethers of cellulose, polyvinyl alcoholsand polyvinyl pyrrolidone.

The negative-acting single sheet color proofing element generallycomprises a carrier having coated thereon in the following order: (a) awater-soluble release layer; (b) a water-soluble photosensitive color;(c) a water-soluble photopolymerizable inter-layer; and (d) awater-emulsion adhesive layer.

The carrier sheet is coated with a water-soluble release layer whichfunctions both as a releasable coating and an oxygen barrier. Thefunction of the release layer is to serve as a parting layer between thecarrier sheet and the photosensitive color coating layer. The releaselayer remains in contact with the photosensitive color layer when thecarrier is removed. The release layer acts as an oxygen barrier toprevent oxygen inhibition of the photopolymerization of thephotopolymers in the photosensitive color layer during the imagingprocess. The preferred material for use in the present invention is a1.5 to 2.0 mil (3.7 to 5.6 cm) polyester film provided with a releaselayer comprising a cellulose methyl ether, polyvinylpyrolidone orpolyvinyl alcohol resin. The release properties of the release layer maybe adjusted by the addition of surfactants. Preferred surfactantsinclude alkylarylpolyether alcohols, such as Triton™ X-100 (octylphenoxyethanol, available from Rohm & Haas, Philadelphia, Pa.), glycerin andethoxylated castor oil. In the preferred embodiment, the surfactant ispresent in the release layer at about 0.1 to 5% by weight of solids inthe layer, more preferably 0.5 to 2%. Other ingredients may be addedsuch as mold inhibitors, anti-halation dyes, filter dyes, solvents,wetting agents, etc. Additionally, the carrier may have a smooth ortextured surface and may also include colorants or UV absorbers.

A photosensitive color layer is coated onto the releasable surface ofthe carrier. This layer typically comprises a crosslinkable acrylatedpolymer (or oligomer), an alkaline soluble resin, a colorant ortexturing material and a photoinitiator. The preferred crosslinkableacrylated polymers have a weight-average molecular weight between 5,000and 100,000, and contain at least one pendant unsaturated acrylategroup. Acrylated polymers having this molecular weight range are usuallyinsoluble in water and are supplied commercially as latexes or wateremulsions. Even though the acrylic latexes and emulsions may form waterinsoluble coatings when used alone, it has been discovered that awater-dispersible photosensitive color layer is formed when combinedwith alkaline soluble resins. Suitable acrylated polymers or oligomersinclude acrylated urethanes, acrylated acrylics, acrylated epoxies,aminoplast derivatives having pendant alpha, beta unsaturated carbonylgroups, isocyanurate derivatives having at least one pendant acrylategroup, isocyanate derivatives having at least one pendant acrylategroup, acrylated polyesters, and mixtures thereof. Suitable commerciallyavailable materials include E-3120 crosslinkable acrylic latex(available from Rohm and Haas, Philadelphia, Pa.), Neorad™ 440crosslinkable acrylic polymer water-emulsion (available from ICI/ZenecaResins, Wilmington, Mass.), Neorad™ 3709 crosslinkable polyurethaneacrylic water-emulsion (available from ICI/Zeneca Resins) and Sancure™850 crosslinkable acrylic water-emulsion (available from B. F. Goodrich,Cleveland, Ohio). Aqueous acrylic polymer emulsions, latexes ordispersions are generally referred to as particles or droplets ofacrylate polymer suspended in water, preferably with the aid of adispersing agent. In the practice of the present invention, the particlesize of the emulsion or latex is preferably between 10 and 10,000 nm,more preferably between 10 and 100 nm.

An alkaline soluble resin is added to the photosensitive color layer tocontrol developablility of the layer. Suitable resins include polyvinylacetate/crotonic acid copolymers, styrene maleic anhydride half esterresins (i.e., Joncryl™ 91 or 142, available from Johnson Wax, Racine,Wis.), polyvinyl alcohols, polyvinyl pyrollidones, and acid modifiedpolyvinyl butyral resins (i.e., condensation products of polyvinylbutyral with succinic anhydride in the presence of triethylamine). Themolecular weight and acid number of the alkaline soluble resin will varydepending upon the particular photopolymerizable acrylic polymer used inthe formulation. If the molecular weight is too low and/or the acidfunctionality too high, then the imaged or cured portion of thephotosensitive layer may be attacked by the developer resulting indensity loss, uneven development around the fringes of the halftonedots, or complete loss of the highlight dots. On the other hand, if themolecular weight is too high and/or the acid functionality too low, thenthe non-imaged portions of the photosensitive layer may not be removedby the developer, resulting in loss of resolution in the shadow areas ofthe proof (90-99.5% dots) or background staining. The strength of thedeveloper can be increased in this particular situation to assist in theremoval of the layer; however, this may lead to loss of the highlightdots. Preferred alkaline soluble resins have a weight-average molecularweight between 1,000 and 200,000 and an acid number between 50 and 300.

In a preferred embodiment, the photoinitiator(s) used preferably doesnot generate a visible color change in the image or adhesive layersafter exposure. Examples of suitable photoinitiators include;halomethyl-1,3,5-triazines, acetophenones, benzophenones, iodoniumsalts, and thioxanthones. Preferred photoinitiators are water-soluble orwater-dispersible. Suitable photoinitiators include water solubleMichelor's ketone, Irgacure™ 2959 (available from Ciba-Geigy, Hawthorne,N.Y.), Quantacure™ ABQ or Quantacure™ QTX (both available from BiddleSawyer, New York, N.Y.), and water-solubletrihalomethyl-1,3,5-triazines. Halomethyl-1,3,5-triazines having anaromatic or aliphatic sulfonic acid group or salt thereof areparticularly useful. Examples of suitable water-solubletrihalomethyl-1,3,5-triazines are described in co-pending U.S. Patentapplication Bonham, J., titled "Ionic Halomethyl-1,3,5-TriazinePhotoinitiators" filed on May 23, 1997 (FN# 52333USA7A), incorporatedherein by reference, and have the following general structure: ##STR2##wherein X is chlorine or bromine; A is an aryl group having 1 to 3rings; L is a linking group selected from the group consisting ofcarbamato, carbamido, amino, amido, alkyl having up to 15 carbon atoms,oxy, alkenyl, alkynyl, keto, ester, sulfonyl, aryl, and combinationsthereof; n is 0 or 1; R³ is an acid group selected from the groupconsisting of sulfonic acid, carboxylic acid, phosphonic acid and saltsthereof; and R² is --CX₃, --NH₂, NHR, --NR₂, --OR, or --R, where R isselected from the group consisting of an alkyl group having up to 15carbon atoms, an aryl group having up to three rings, a heterocyclicaromatic group, and combinations thereof. A preferred water-solublephotoinitiator is the reaction product of2,4-bis(trichloromethyl)-6-[3-(2-hydroxyethoxy)styryl]-1,3,5-triazincwith 2-sulfobenzoic acid cyclic anhydride.

Other examples of useful water-soluble trihalomethyl-1,3,5-triazines aredescribed in JP 63-298339 which include trihalomethyl-1,3,5-triazineshaving the following general structure: ##STR3## where R₁ is acarboxylate group, a sulfonate group, an alkyl group, or an alkylsubstituted amino group; R₂ and R₃ are each hydrogen, carboxylate group,sulfonate group, alkyl group, or alkyl substituted amino group which maybe the same or different with each other; X and Y are each chlorine orbromine; and m and n are each 0, 1, or 2.

The photoinitiators may be used singly or in combination with eachother. The optimum amount of initiator will be dependent upon theoligomer type used and the filtering effect of the pigment used;however, the initiator is usually present in concentrations of about1.0-15% by weight of the photosensitive composition. When triazines areused as the photoinitiator, the photosensitive color coating solution ispreferably less than a pH of 7.5. Some triazine initiators have atendency to decompose in alkaline environments. In preparing thephotosensitive color coating solution, the triazine is added last sothat the pH of the coating solution may be adjusted to below 7.5 (ifnecessary) before adding the triazine. If the pH of the solution is tohigh, the pH of the solution is decreased by adding an acid (e.g., HCl)before adding the triazine initiator.

Pigments or dyes may be used as colorants in the photosensitive colorlayer. However, pigments or polymeric dyes are preferred since they havea lower tendency for migration between the layers. Pigments are morepreferred due to the wide variety of colors available and lower cost.Pigments are generally introduced into the photosensitive formulation inthe form of a millbase comprising the pigment dispersed with a binderand suspended into water with the aid of a dispersant. The dispersionprocess may be accomplished by a variety of methods well known in theart, such as two-roll milling, three-roll milling, sand milling, ballmilling, etc. Many different pigments are available and are well knownin the art. The pigment type and color are chosen such that the coatedcolor proofing element is matched to a preset color target orspecification set by the industry. Color enhancing additives may be usedwhich include fluorescent, pearlescent, iridescent, and metallicmaterials. Texturing materials such as silica, polymeric beads,reflective and non-reflective glass beads, or mica may also be added inplace of a colorant to provide an image with a textured appearance. Thecolor enhancing additives or texturing materials may be used eitheralone or in combination with the above pigments to produce proofs withthe desired visual effects.

The type of dispersing resin and the pigment to resin composition ratiochosen are dependent upon the pigment type, surface treatment on thepigment, dispersing solvent and milling process. Some examples of resinssuitable for generating millbases which are compatible with theaforementioned photo-oligomers and monomers include; polyvinylacetate/crotonic acid copolymers, styrene/maleic anhydride partial-esterresins, acid containing acrylic and methacrylic polymers and copolymers,polyvinyl acetals, polyvinyl acetals modified with anhydrides andamines, hydroxy alkyl cellulose resins, acrylic resins having pendantquaternary ammonium and/or alkyl hydroxy groups andstyrene/acrylic/acrylic acid resins. The dispersion may contain amixture of these resins. The pigment to resin ratio in the dispersion istypically between 0.6 to 5.0, preferably between 0.8 to 3.0. Preferredcommercially available aqueous pigment dispersions include Sunsperse™aqueous dispersions available from Sun Chemical, Cincinnati, Ohio.

A dispersing agent may be necessary to achieve optimum dispersionquality. Some examples of dispersing agents include; polyester/polyaminecopolymers, alkylarylpolyether alcohols, acrylic resins and Disperbyk™wetting agents available from Byk-Chemie USA, Wallingford, Conn. Othercomponents may also be included in the millbase such as surfactants toimprove solution stability, fluorescent materials, optical brighteners,UV absorbers, fillers, etc.

Additional binders may also be included in the photosensitive colorformulation to balance developability and tack for each color. Thecoating weights of the individual colors may vary in order to achievethe preset color target. The color formulations are adjusted to achieveoptimum color, resolution, exposure speed and developability. Typicaldry color coating weights are between 50 mg/ft² and 150 mg/ft² (0.54g/m² and 1.61 g/m²), preferred 60 mg/ft² and 90 mg/ft² (0.65 g/m² and0.97 g/m²).

Coated adjacent to the photosensitive color layer is aphotopolymerizable inter-layer. The inter-layer may be the same solutionused for the photosensitive color layer without the colorant or it maybe any photopolymerizable composition that is soluble in water andrendered insoluble in water upon exposure to ultraviolet radiation. Thephotopolymerizable inter-layer is present to prevent interaction betweenthe color layer and the adhesive, and also improves developability ofthe non-image areas. The inter-layer typically comprises anphotopolymerizable ethylenically unsaturated compound, an acidic binderand a photoinitiator. Basically the same materials as those describedfor the photosensitive color layer may be used in the inter-layer. Theethylenically unsaturated compound is present at about 50-80% by weightof the total inter-layer composition. Preferred binders include;polyvinyl acetate/crotonic acid copolymers, styrene/maleic anhydridepartial-ester resins, acid containing acrylic and methacrylic polymersand copolymers, acidified polyvinyl acetals, and styrene/acrylic/acrylicacid resins. The acidic binder or resin is present at about 15-50% byweight of the total inter-layer composition. The initiator is present at0-10% by weight of the total inter-layer composition. The addition ofphotoinitiator may be unnecessary depending upon the extent upon whichthe inter-layer intermixes with the adjacent photosensitive color layer.The inter-layer is coated to a dry coating weight of about 0.15 to 2.0g/m², preferably about 0.2 to 1.0 g/m².

Coated adjacent to the photopolymerizable inter-layer is a waterinsoluble adhesive layer. The adhesive layer provides a means oflaminating the color proofing element to a temporary or permanentsubstrate under heat and pressure. Examples of adhesive coating solventsinclude alcohols, water and hydrocarbon solvents. Because hydrocarbonsolvents like heptane and naphtha are prone to irregular coatingpatterns, due primarily to static, more polar solvents such as water andalcohols are preferred, more preferably water-emulsions or latexes. Theadhesive is preferably a thermally activated adhesive that is softenableat a temperature of less than 200° C., preferably within a range between100° C. and 160° C. In contrast with the softening characteristics ofthe adhesive, it is desirable that the adhesive not block during storageor shipment. Resins having a Tg between 45° C. and 60° C., includingcopolymers and terpolymers of alkyl acrylate, alkyl methacrylate,styryl, and acrylamide monomers, meet both the lamination criteria andavoid the potential for blocking, without requiring the use of anadditional protective liner. Useful resins include polymers, copolymersand terpolymers of methyl methacrylate, n-butyl methacrylate,n-butyl/isobutyl methacrylate, vinylacetates, N-(hydroxymethyl)acrylamide and styrenes. Vinyl acetate polymers have been found to bevery sensitive to moisture and can cause blocking of the coatedmaterials in shipment and storage if the vinyl acetate component of theadhesive is present in amounts greater than 20%. Other additives may bepresent to aid in coating and performance such as surfactants,coalescent aids, plasticizers, slip agents (i.e., polymethacrylate beadslike those described in U.S. Pat. No. 4,885,225, silica, polyethylenewaxes), optical brighteners, UV absorbers, etc.

A multi-colored proof is made by laminating a color proofing elementonto a receptor. The carrier may be removed either prior to exposure orprior to the development step. The laminated structure is imaged througha negative color separation graphic art film corresponding to the colorof the proofing element to create a latent image. The spectral and poweroutput of the exposure unit and the absorption of the photoinitiatorsystem are chosen for an optimum exposure speed. Typical exposure unitsare equipped with UV lamps having optimum spectral outputs between 250nm and 500 nm and a power output between 2.5 and 10 Kilowatts. Theexposed laminated structure is then developed with an aqueous developer.The process of laminating, exposing and developing is then repeatedusing a different color until the desired multi-colored composite proofis complete. A non-colored or textured image may be added if so desiredby laminating, exposing and developing a proofing element whosephotosensitive layer contains texturing materials such as thosedescribed earlier in place of or in addition to a colorant.

The receptor may be a permanent substrate. A suitable composition forthe receptor sheet is a heat stable, waterproof white paper, such asMatchprint™ base (available from Imation Corp.™, Oakdale, Minn.). Thereceptor sheet may also be a polyester film or any other heat stableplastic material. Alternatively, the receptor may be a temporaryreceptor such as those described in U.S. Pat. Nos. 5,240,810; 5,192,630;and 5,094,931.

Suitable aqueous developer solutions have a pH between 7 and 9,including ordinary warm tap water. When tap water is used, it may benecessary to add a water conditioner, a water soluble surfactant orother additives to compensate for the variations in the quality of thewater. If the water contains high levels of minerals, it may also benecessary to pre-filter the water through a commercial water filteringsystem. It may be desirable to buffer the developer to a specific pH byadding a combination of sodium or potassium carbonate, and sodium orpotassium bicarbonate. Preferred buffered solutions contain about0.5-2.0% by weight of carbonate, about 0-1.0% by weight of bicarbonate,and about 0.1-1.0% by weight of a surfactant dissolved in water.Preferred surfactants nonexclusively include; Surfynol™ 465 (ethoxylatedtetramethyl decynediol, available from Air Products and Chemicals,Allentown, Pa.), Surfactol™ 365 (ethoxylated castor oil, available fromCasChem Inc., Bayonne, N.J.), Triton™ X-100(octylphenoxypolyethoxyethanol, available from Rohm and Haas,Philadelphia, Pa.), and Surfynol™ GA. (acetylenic diols compounded withother non-ionic surfactants and solvents, available from Air Productsand Chemicals, Allentown, Pa.).

The invention will now be illustrated in the following non-limitingexamples:

EXAMPLES

Unless designated otherwise, all chemical raw materials are availablefrom Aldrich Chemicals, Milwaukee, Wis. Sunsperse™ pigment dispersionsare available from Sun Chemicals, Cincinnati, Ohio.

The following preparation describes the method for preparing thewater-soluble triazine initiator referred to in the Examples.

Water-soluble Triazine Initiator

A slurry of 216.5 g (0.0.453 eq) of2,4-bis(trichloromethyl)-6-[3-(2-hydroxyethoxy)styryl]-1,3,5-triazine in1400 mL of toluene was prepared and the water impurity was removed byazeotropic distillation of approximately 100 ml of the solvent. Aftercooling to room temperature, 100 g (0.543 eq) of 2-sulfobenzoic acidanhydride (Aldrich Chemical) was added. The solution was heated to 70°C. and the reaction was complete in about 3 hrs. as determined by FTIRand TLC. After cooling to room temperature, the reaction solution wasfiltered to remove a small amount of a brown impurity. The filtrate wasthen slowly poured into a solution of 5000 mL heptane/1000 mL 2-propanolwith rapid stirring at 10° C. The product precipitated and was collectedby filtration. A rubber dam was used during the filtration to helpremove excess solvent. After drying at 50-60° C., 247.5 g (83% yield) ofa slightly yellow, deliquescent solid was collected. The productdissolved in water at a concentration of at least 10%, and was verysoluble in a wide variety of organic solvents such as methanol, acetone,ethyl acetate, chloroform, and toluene. The structural formula of theproduct was confirmed by NMR and FTIR to be the trichloromethyltriazinecompound with a sulfonic acid group illustrated below: ##STR4##

Examples 1-8

Examples 1-8 illustrate water coatable and water developable overlaynegative-acting color proofing elements.

The preparation for the water-soluble oxygen barrier layer coatingsolution used in Examples 1-8 is described below.

    ______________________________________                                        Water-Soluble Oxygen Barrier Layer Coating Solution                           ______________________________________                                        Airvol ™ 540 Polyvinyl alcohol                                                                       843 g                                               (available from Air Products and Chemicals,                                   Allentown, PA)                                                                Airvol ™ 205 Polyvinyl alcohol                                                                       2,458 g                                             (available from Air Products and Chemicals,                                   Allentown, PA)                                                                PVP K-90 (polyvinyl pyrolidone,                                                                         2,298 g                                             available from GAF Chemical Corporation,                                      Wayne, NJ)                                                                    Kathon ™ CG/ICP Preservative                                                                         5.8 g                                               (available from Rohm and Haas, Philadelphia, PA)                              Stearyl methacrylate/hexanediol diacrylate Beads                                                        15.0 g                                              Deionized Water           11,379 g                                            ______________________________________                                    

Example 1

This example illustrates a water-soluble magenta overlay construction. Amagenta color solution was prepared by adding 0.5 g Sunsperse™ Reddispersion (47.1% Red 48:1 pigment in water) to 5.0 g of the followingphotopolymer solution.

    ______________________________________                                        Water                     14.0 g                                              Water-Soluble Triazine initiator                                                                        0.11 g                                              Joncryl ™ 91 (27% T.S. acrylic colloidal solution,                                                   0.79 g                                              available from Johnson Wax, Racine WI)                                        E-3120 (41% T.S. UV Cross Iinking Latex,                                                                5.07 g                                              available from Rohm and Haas, Philadelphia, PA)                               ______________________________________                                    

The aqueous magenta solution was coated onto a 2.65 mil (0.07 mm)polyester substrate (ICI 054 film, available from ICI Americas Inc.,Wilmington, Del.) with a #12 wire wound bar and dried for 2 minutes at93° C. (200° F.) resulting in a dry coating thickness of approximately0.35 mils (8.9 microns). The magenta color layer was then overcoatedwith the oxygen barrier layer described above using a #6 wire wound barand dried for 2 minutes at 93° C. (200° F.).

The magenta overlay element was exposed under vacuum through a UGRAplate control target (available from EMPA/UGRA, St. Gallen, Switzerland)with a UV light source having a power output of 0.15 Watt/cm². Theimaged materials were developed using a buffered aqueous developercomprising 1% potassium carbonate, 1% potassium bicarbonate and 0.1%Surfynol™ 465 (ethoxylated tetramethyldecynediol surfactant, availablefrom Air Products, Allentown, Pa.) in water. The developed image had adot size and line resolution as small as 50 microns.

Example 2

This example illustrates a water-soluble magenta overlay construction. Amagenta color solution was prepared by adding 0.5 g of Sunsperse™Magenta dispersion (38.9% dispersion of Red 122 Quindo Magenta pigmentin water) to 5.0 g of the following photopolymer solution.

    ______________________________________                                        Water                      14.0 g                                             Water-Soluble Triazine Initiator                                                                         0.11 g                                             Joncryl ™ 91 (acrylic colloidal solution)                                                             1.39 g                                             Neorad ™ 440 (UV Cross linking dispersed polymer,                                                     3.80 g                                             available from ICI/Zeneca Resins, Wilmington, Mass.)                          ______________________________________                                    

The aqueous magenta solution was coated onto a 2.65 mil (0.07 mm) ICI054 polyester substrate with a #6 wire wound bar and dried for 2 minutesat 93° C. (200° F.) resulting in a dry coating thickness ofapproximately 0.35 mils (8.9 microns). The magenta color layer was thenovercoated with the oxygen barrier layer described above using a #6 wirewound bar and dried for 2 minutes at 93° C. (200° F.).

The magenta overlay color proofing element was exposed under vacuumthrough a UGRA plate control target with a UV light source having apower output of 0.15 Watt/cm². The imaged materials were developed usingthe same buffered aqueous solution described in Example 1. The developedimage had a dot size and line resolution as small as 50 microns.

Example 3

This example illustrates a water-soluble cyan overlay construction. Acyan color solution was prepared by adding 0.25 g of Sunsperse™ Bluedispersion (51.1% dispersion of 15:3 Phthalo Blue pigment in water) to5.0 g of the photopolymer solution described in Example 2. The aqueouscyan solution was coated onto a 2.65 mil (0.07 mm) ICI 054 polyestersubstrate with a #6 wire wound bar and dried for 2 minutes at 93° C.(200° F.) resulting in a dry coating thickness of approximately 0.35mils (8.9 microns). The cyan color layer was then overcoated with theoxygen barrier layer described above using a #6 wire wound bar and driedfor 2 minutes at 93° C. (200° F.).

The cyan overlay color proofing element was exposed under vacuum througha UGRA plate control target with a UV light source having a power outputof 0.15 Watt/cm². The imaged materials were developed using the samebuffered aqueous solution described in Example 1. The developed imagehad a dot size and line resolution as small as 50 microns.

Example 4

This example illustrates a water-soluble black overlay construction. Ablack color solution was prepared by adding 0.46 g of Sunsperse™ Blackdispersion (49.1% dispersion of Carbon Black 7 pigment in water with apH of 8-9) to 10.0 g of the photopolymer solution described in Example2. The aqueous black solution was coated onto a 2.65 mil (0.07 mm) ICI054 polyester substrate with a #6 wire wound bar and dried for 2 minutesat 93° C. (200° F.) resulting in a dry coating thickness ofapproximately 0.35 mils (8.9 microns). The black color layer was thenovercoated with the oxygen barrier layer described above using a #6 wirewound bar and dried for 2 minutes at 93° C. (200° F.).

The black overlay color proofing element was exposed under vacuumthrough a UGRA plate control target with a UV light source having apower output of 0.15 Watt/cm². The imaged materials were developed usingthe same buffered aqueous solution described in Example 1. The developedimage had a dot size and line resolution as small as 50 microns.

Example 5

A magenta color solution was prepared by first mixing 9.41 g ofSunsperse™ Red dispersion (47.1% Red 48:1 pigment in water), 0.25 g ofSunsperse™ Yellow (47.9% Yellow 14 pigment in water) and 0.25 g ofSunsperse™ Yellow (33.0% Yellow 13 pigment in water). Under lightagitation, 75.42 g of deionized water followed by 19.51 g of Neorad™ 440and 3.25 g of Joncryl™ 142 was added. The pH measured approximately 6.9to 7.2. Finally, 51.92 g of a 1% solution of water-soluble triazineinitiator was added to the colored solution. The aqueous magentasolution was extrusion coated onto a 2.65 mil (0.07 mm) ICI 054polyester substrate and dried at 93° C. (200° F.) resulting in a drycoating weight of 0.65 g/m² (60 mg/ft²). The magenta color layer wasthen overcoated with the oxygen barrier coating solution described aboveand dried at 93° C. (200° F.) resulting in a dry coating weight of 0.54g/m² (50 mg/ft²).

The magenta overlay construction was exposed under vacuum through a UGRAplate control target with a UV light source having a power output of0.15 Watt/cm². The imaged materials were developed using a bufferedaqueous developer comprising 1% potassium carbonate, 1% potassiumbicarbonate and 0.1% Surfynol™ 465 (ethoxylated tetramethyldecynediolsurfactant, available from Air Products, Allentown, Pa.) in water. Theresultant image resolved 1% highlight halftone dots and 99% shadowhalftone dots.

The imaged materials were also developed in a 2.6% by weight aqueoussolution of Triton™ X-100 in water at 80° F. The resultant imageresolved 2% highlight halftone dots and 98% shadow halftone dots using a150 lpi UGRA target.

Example 6

A cyan color solution was prepared by first mixing 4.13 g of Sunsperse™Blue dispersion (51.1% Blue 15:3 pigment in water), 5.12 g of Sunsperse™Blue dispersion (50.9% Blue 15 pigment in water), and 0.39 g ofSunsperse™ Yellow dispersion (33.0% Yellow 83 pigment in water). Underlight agitation, 60.08 g of deionized water followed by 23.58 g ofNeorad™ 440 and 3.93 g of Joncryl™ 142 was added. The pH measuredapproximately 6.8 to 7.2. Finally, 62.76 g of a 1% solution ofwater-soluble triazine initiator was added to the colored solution. Theaqueous cyan solution was extrusion coated onto a 2.65 mil (0.07 mm) ICI054 polyester substrate and dried at 93° C. (200° F.) resulting in a drycoating weight of 0.86 g/m² (80 mg/ft²). The cyan color layer was thenovercoated with the oxygen barrier coating solution described above anddried at 93° C. (200° F.) resulting in a dry coating weight of 0.54 g/m²(50 mg/ft²).

The cyan overlay construction was exposed under vacuum through a UGRAplate control target with a UV light source having a power output of0.15 Watt/cm². The imaged materials were developed using a bufferedaqueous developer comprising 1% potassium carbonate, 1% potassiumbicarbonate and 0.1% Surfynol™ 465 in water. The resultant imageresolved 1% highlight halftone dots and 99% shadow halftone dots.

The imaged materials were also developed in a 2.6% by weight aqueoussolution of Triton™ X-100 in water at 80° F. The resultant imageresolved 2% highlight halftone dots and 98% shadow halftone dots using a150 lpi UGRA target.

Example 7

A yellow color solution was prepared by first charging 3.93 g ofSunsperse™ Yellow dispersion (33.0% Yellow 83 pigment in water) into amixing vessel. Under light agitation, 101.92 g of deionized waterfollowed by 14.15 g of Neorad™ 440 and 2.36 g of Joncryl™ 142 was added.The pH measured approximately 6.8 to 7.2. Finally, 37.66 g of a 1%solution of water-soluble triazine initiator was added to the coloredsolution. The aqueous yellow solution was extrusion coated onto a 2.65mil (0.07 mm) ICI 054 polyester substrate and dried at 93° C. (200° F.)resulting in a dry coating weight of 0.65 g/m² (60 mg/ft²). The yellowcolor layer was then overcoated with the oxygen barrier coating solutiondescribed above and dried at 93° C. (200° F.) resulting in a dry coatingweight of 0.54 g/m² (50 mg/ft²).

The yellow overlay construction was exposed under vacuum through a UGRAplate control target with a UV light source having) a power output of0.15 Watt/cm². The imaged materials were developed using a bufferedaqueous developer comprising 1% potassium carbonate, 1% potassiumbicarbonate and 0.1% Surfynol™ 465 in water. The resultant imageresolved 1% highlight halftone dots and 99% shadow halftone dots.

Example 8

A black color solution was prepared by first charging 7.63 g ofSunsperse™ Black dispersion (49.1% Black 7 pigment in water) into amixing vessel. Under light agitation, 43.47 g of deionized waterfollowed by 25.05 g of Neorad™ 440 and 4.86 g of Joncryl™ 142 was added.The pH measured approximately 6.8 to 7.2. Finally, 88.99 g of a 1%solution of water-soluble triazine initiator was added to the coloredsolution. The aqueous black solution was extrusion coated onto a 2.65mil (0.07 mm) ICI 054 polyester substrate and dried at 93° C. (200° F.)resulting in a dry coating weight of 0.97 g/m² (90 mg/ft²). The blackcolor layer was then overcoated with the oxygen barrier coating solutiondescribed above and dried at 93° C. (200° F.) resulting in a dry coatingweight of 0.54 g/m² (50 mg/ft²).

The black overlay construction was exposed under vacuum through a UGRAplate control target with a UV light source having a power output of0.15 Watt/cm². The imaged materials were developed using a bufferedaqueous developer comprising 1% potassium carbonate, 1% potassiumbicarbonate and 0.1% Surfynol™ 465 in water. The resultant imageresolved 1% highlight halftone dots and 99% shadow halftone dots.

The imaged materials were also developed in a 2.6% by weight aqueoussolution of Triton™ X-100 in water at 80° F. The resultant imageresolved 2% highlight halftone dots and 98% shadow halftone dots using a150 lpi UGRA target.

Examples 9-12

Examples 9-12 illustrate water coatable and water developable singlesheet color negative-acting proofing elements.

The following preparations describe methods for preparing coatingsolutions used in Examples 9-12.

    ______________________________________                                        Water-Soluble Release Layer Coating Solution                                  Airvol ™ 540 Polyvinyl alcohol                                                                        843 g                                              (available from Air Products and Chemicals,                                   Allentown, PA)                                                                Airvol ™ 205 Polyvinyl alcohol                                                                        1,458 g                                            (available from Air Products and Chemicals,                                   Allentown, PA)                                                                PVP K-90 (polyvinyl pyrolidone,                                                                          2,298 g                                            available from GAF Chemicals Corporation, Wayne, NJ)                          Kathon ™ CG/ICP Preservative                                                                          5.8 g                                              (available from Rohm and Haas, Philadelphia, PA)                              Deionized Water            11,379 g                                           Water-Emulsion Adhesive Coating Solution                                      Synthemul ™ R-97603 (terpolymer of N-(hydroxymethyl)                                                  13,511 g                                           acrylamide/butyl acrylate/methyl methacrylate,                                available from Reichhold Chemicals Inc., Dover, DE;                           45% total solids in water)                                                    Deionized Water            4320 g                                             Tetronic ™ 701 (alkoxylated amine non-ionic surfactant,                                               16 g                                               available from BASF Corporation, Parsippany, NJ)                              10.5 Micron Polymethyl methacrylate beads                                                                22 g                                               (prepared as described in U.S. Pat. No. 2,701,245)                            Daxad ™ 11KLS Dispersant (potassium salt of polymerized                                               1.3 g                                              naphthalene sulfonic acid, available from W. R. Grace,                        Lexington, Mass.)                                                             ______________________________________                                    

Example 9

This example describes a water developable magenta single sheet colorproofing element. The release coating solution described above wascoated onto 2 mil (0.051 mm) polyester film using a #12 wire wound barand dried for 2 minutes at 93° C. (200° F.). A magenta color solutionwas prepared by adding 0.25 g of Sunsperse™ Red dispersion (47.1% Red48:1 pigment in water) to 5.0 g of the following photopolymer Asolution.

    ______________________________________                                        Photopolymer A solution                                                       ______________________________________                                        Water                  22.31 g                                                Water-Soluble Triazine Initiator                                                                     0.16 g                                                 Joncryl ™ 91 (acrylic colloidal solution)                                                         2.09 g                                                 B-3120 (UV Cross linking Latex)                                                                      5.44 g                                                 ______________________________________                                    

The magenta color solution was coated onto the release layer using a #6wire wound bar and dried for 2 minutes at 93° C. (200° F.). The magentacolor layer was then overcoated with the photopolymer A solution(without the added pigment dispersion) using a #6 wire wound bar anddried for 2 minutes at 93° C. (200° F.). The adhesive solution describedabove was then coated onto the photopolymer layer with a #12 wire woundbar and dried at 93° C. (200° F.).

The magenta single sheet construction was laminated onto a Matchprint™paper base (available from Imation Corp.™, Oakdale, Minn.), thepolyester removed and then exposed under vacuum through a UGRA platecontrol target. The materials were exposed with a UV light source havinga power output of 0.15 Watt/cm². The imaged materials were developedusing a buffered aqueous developer comprising 1% potassium carbonate, 1%potassium bicarbonate and 0.1% Surfynol™ 465 in water. The developedimage had a dot size and line resolution as small as 50 microns.

Example 10

This example describes a water developable cyan single sheet colorproofing element. The release coating solution described above wascoated onto 2 mil (0.051 mm) polyester film using a #12 wire wound barand dried for 2 minutes at 93° C. (200° F.). A cyan color solution wasprepared by adding 0.5 g of Sunsperse™ Blue dispersion (51.1% dispersionof 15:3 Phthalo Blue pigment in water) to 10.0 g of the followingphotopolymer B solution.

    ______________________________________                                        Photopolymer B solution                                                       ______________________________________                                        Water                      14.0 g                                             Water-Soluble Triazine Initiator                                                                         0.11 g                                             Joncryl ™ 91 (acrylic colloidal solution)                                                             1.39 g                                             Neorad ™ 440 (UV Cross linking dispersed polymer)                                                     3.80 g                                             ______________________________________                                    

The cyan color solution was coated onto the release layer using a #4wire wound bar and dried for 2 minutes at 93° C. (200° F.). The cyancolor layer was then overcoated with the photopolymer B solution(without the added pigment dispersion) using a #4 wire wound bar anddried for 2 minutes at 93° C. (200° F.). The adhesive solution describedabove was then coated onto the photopolymer layer with a #10 wire woundbar and dried at 93° C. (200° F.).

The cyan single sheet construction was laminated onto a Matchprint™paper base (available from Imation Corp.™, Oakdale, Minn.), thepolyester removed and then exposed under vacuum through a UGRA platecontrol target. The materials were exposed with a UV light source havinga power output of 0.15 Watt/cm². The imaged materials were developedusing a buffered aqueous developer comprising 1% potassium carbonate, 1%potassium bicarbonate and 0.1% Surfynol™ 465 in water. The developedimage had a dot size and line resolution as small as 50 microns.

Example 11

This example describes a water developable black single sheet colorproofing element. The release coating solution described above wascoated onto 2 mil (0.051 mm) polyester film using a #12 wire wound barand dried for 2 minutes at 93° C. (200° F.). A black color solution wasprepared by adding 0.5 g Sunsperse™ Black dispersion (49.1% dispersionof Carbon Black 7 pigment in water at a pH of 8-9, available from SunChemical, Cincinnati, Ohio) to 10.0 g of the photopolymer B solutiondescribed in Example 6. The black color solution was coated onto therelease layer using a #4 wire wound bar and dried for 2 minutes at 93°C. (200° F.). The black color layer was then overcoated with thephotopolymer B solution described in Example 6 (without the addedpigment dispersion) using a #4 wire wound bar and dried for 2 minutes at93° C. (200° F.). The adhesive solution described above was then coatedonto the photopolymer layer with a #10 wire wound bar and dried at 93°C. (200° F.).

The black single sheet construction was laminated onto a Matchprint™paper base (available from Imation Corp.™, Oakdale, Minn.), thepolyester removed and then exposed under vacuum through a UGRA platecontrol target. The materials were exposed with a UV light source havinga power output of 0.15 Watt/cm². The imaged materials were developedusing a buffered aqueous developer comprising 1% potassium carbonate, 1%potassium bicarbonate and 0.1% Surfynol™ 465 in water. The developedimage had a dot size and line resolution as small as 50 microns.

Example 12

The following example illustrates a single sheet color proofing elementwhich is capable of being developed in a buffered aqueous developer. Thefollowing release layer coating solution was extrusion coated onto a 2.0mil (0.051 mm) polyester substrate and dried at 93° C. (200° F.)resulting in a dry coating weight of 0.54 g/m² (50 mg/ft²).

    ______________________________________                                        Water-Soluble Release Layer Coating Solution                                  ______________________________________                                        PVP K-90 (polyvinyl pyrrolidone; 7.5% total solids in water)                                               750.0 g                                          Deionized Water              900.0 g                                          Surfactol ™ 365 (ethoxylated castor oil, available from                                                 350.0 g                                          CasChem Inc., Bayonne, NJ; 1.0% total solids in water)                        ______________________________________                                    

A Cyan color solution was prepared by first mixing 4.47 g of Sunsperse™Blue dispersion (51.1% solids Blue 15:3 pigment in water), 5.54 g ofSunsperse™ Blue dispersion (50.9% Blue 15 pigment in water), and 0.42 gof Sunsperse™ Yellow dispersion (33.0% Yellow 83 pigment in water).Under light agitation, 66.17 g of deionized water was added followed by25.92 g of Neorad™ 440 acrylic polymer, and 4.32 g of Joncryl™ 142acrylic resin (available from Johnson Wax, Racine, Wis.). The pHmeasured approximately 6.8 to 7.2. Finally, 68.97 g of a 1% aqueoussolution of water-soluble triazine initiator was added to the coloredsolution. The aqueous cyan solution was extrusion coated over therelease layer described above and dried at 93° C. (200° F.) resulting ina dry coating weight of 0.86 g/m² (80 mg/ft²).

A photopolymerizable inter-layer coating solution was prepared by mixing12.11 g of water with 1.28 g of Neorad™ 440, 0.21 g of Joncryl™ 142, and3.39 g of a 1% aqueous solution of water-soluble triazine initiator. Theinter-layer solution was then extrusion coated over the cyan color layerand dried at 93° C. (200° F.) resulting in a coating weight of 0.32 g/m²(30 mg/ft²).

The Water-Emulsion adhesive coating solution described above wasextrusion coated onto the inter-layer and dried at 93° C. (200° F.)resulting in a coating weight of 7.0 g/m² (650 mg/ft²).

The cyan color proofing element was laminated onto a Matchprint™ paperbase, the polyester removed and then exposed under vacuum through a UGRAplate control target. The materials were exposed with a UV light sourcehaving a power output of 0.15 Watt/cm². The imaged materials weredeveloped using a developer comprising 1% potassium carbonate, 1%potassium bicarbonate and 0.1% Surfynol™ 465 (ethoxylatedtetramethyldecynediol surfactant, available from Air Products) in water.The resultant image resolved 3% highlight halftone dots and 97% shadowhalftone dots.

Reasonable variations and modifications are possible from the foregoingdisclosure without departing from either the spirit or scope of theinvention as claimed.

What is claimed:
 1. A color proofing element comprising a carrier havingdeposited thereon, in the following order:(a) a water-soluble orwater-dispersible photosensitive color layer comprising(i) an acrylatedpolymer having at least one pendant unsaturated acrylate group and aweight-average molecular weight between 5,000 and 100,000; (ii) analkaline soluble resin having a weight-average molecular weight between1,000 and 200,000 and an acid number between 50 and 300; (iii) acolorant; and (iv) a water-soluble or water-dispersible triazinephotoinitiator having the general structure: ##STR5## wherein: X ischlorine or bromine;R¹ is selected from the group consisting ofhydrogen, trichloromethyl, tribromomethyl, aryl, and alkyl having up to15 carbon atoms; L is a linking group selected from the group consistingof carbamato, carbamido, amino, amido, alkyl having up to 15 carbonatoms, oxy, alkenyl, alkynyl, keto, ester, sulfonyl, aryl, andcombinations thereof; and A is a group selected from sulfonic acid,carboxylic acid, phosphonic acid and salts thereof; and (b) awater-soluble or water-dispersible oxygen barrier layer,wherein saidphotosensitive color layer is rendered insoluble and indispersible in anaqueous developer upon exposure to radiation.
 2. The color proofingelement of claim 1 wherein said photosensitive color layer furthercomprises a color enhancing additive.
 3. The color proofing element ofclaim 2 wherein said color enhancing additive is selected from the groupconsisting of fluorescent, pearlescent, iridescent, and metallicmaterials.
 4. A color proofing element comprising a carrier havingdeposited thereon, in the following order:(a) a water-soluble orwater-dispersible photosensitive color layer comprising(i) an acrylatedpolymer having at least one pendant unsaturated acrylate group and aweight-average molecular weight between 5,000 and 100,000; (ii) analkaline soluble resin having a weight-average molecular weight between1,000 and 200,000 and an acid number between 50 and 300; (iii) atexturing material; and (iv) a water-soluble or water-dispersibletriazine photoinitiator having the general structure: ##STR6## wherein:X is chlorine or bromine;R¹ is selected from the group consisting ofhydrogen, trichloromethyl, tribromomethyl, aryl, and alkyl having up to15 carbon atoms; L is a linking group selected from the group consistingof carbamato, carbamido, amino, amido, alkyl having up to 15 carbonatoms, oxy, alkenyl, alkynl, keto, ester, sulfonyl, aryl, andcombinations thereof; and A is a group selected from sulfonic acid,carboxylic acid, phosphonic acid and salts thereof; and (b) awater-soluble or water-dispersible oxygen barrier layer, where in saidphotosensitive color layer is rendered insoluble and indispersible in anaqueous developer upon exposure to radiation.
 5. The color proofingelement of claim 4 wherein said texturing material is selected from thegroup consisting of silica, polymeric beads, reflective glass beads,non-reflective glass beads and mica.
 6. The color proofing element ofclaim 4 further comprising a colorant.
 7. The color proofing element ofclaim 6 further comprising a color enhancing additive.
 8. The colorproofing element of claim 7 wherein said color enhancing additive isselected from the group consisting of fluorescent, pearlescent,iridescent, and metallic materials.
 9. A negative-acting color proofingelement comprising a carrier having coated thereon, in the followingorder:(a) a water-soluble or water-dispersible release layer; (b) awater-soluble or water-dispersible photosensitive color layercomprising(i) an acrylated polymer having at least one pendantunsaturated acrylate group and a weight-average molecular weight between5,000 and 100,000; (ii) an alkaline soluble resin having aweight-average molecular weight between 1,000 and 200,000 and an acidnumber between 50 and 300; (iii) a colorant; and (iv) a water-soluble orwater-dispersible triazine photoinitiator having the general structure:##STR7## wherein: X is chlorine or bromine;R¹ is selected from the groupconsisting of hydrogen, trichloromethyl, tribromomethyl, aryl, and alkylhaving up to 15 carbon atoms; L is a linking group selected from thegroup consisting of carbamato, carbamido, amino, amido, alkyl having upto 15 carbon atoms, oxy, alkenyl, alkynyl, keto, ester, sulfonyl, aryl,and combinations thereof; and A is a group selected from sulfonic acid,carboxylic acid, phosphonic acid and salts thereof; (c) a water-solubleor water-dispersible photopolymerizable inter-layer; and (d) awater-emulsion adhesive layer,wherein said photosensitive color layerand said photopolymerizable inter-layer are rendered insoluble andindispersible in an aqueous developer upon exposure to radiation. 10.The negative-acting color proofing element of claim 9 further comprisinga color enhancing additive.
 11. The color proofing element of claim 10wherein said color enhancing additive is selected from the groupconsisting of fluorescent, pearlescent, iridescent, and metallicmaterials.
 12. A negative-acting color proofing element comprising acarrier having coated thereon, in the following order:(a) awater-soluble or water-dispersible release layer; (b) a water-soluble orwater-dispersible photosensitive color layer comprising(i) an acrylatedpolymer having at least one pendant unsaturated acrylate group and aweight-average molecular weight between 5,000 and 100,000; (ii) analkaline soluble resin having a weight-average molecular weight between1,000 and 200,000 and an acid number between 50 and 300; (iii) atexturing material; and (iv) a water soluble or water-dispersibletriazine photoinitiator having the general structure: ##STR8## wherein:X is chlorine or bromine;R¹ is selected from the group consisting ofhydrogen, trichloromethyl, tribromomethyl, aryl, and alkyl having up to15 carbon atoms; L is a linking group selected from the group consistingof carbamato, carbamido, amino, amido, alkyl having up to 15 carbonatoms, oxy, alkenyl, alkynyl, keto, ester, sulfonyl, aryl, andcombinations thereof; and A is a group selected from sulfonic acid,carboxylic acid, phosphonic acid and salts thereof; (c) a water-solubleor water-dispersible photopolymerizable inter-layer; and (d) awater-emulsion adhesive layer,wherein said photosensitive color layerand said photopolymerizable inter-layer are rendered insoluble andindispersible in an aqueous developer upon exposure to radiation. 13.The color proofing element of claim 12 wherein said texturing materialis selected from the group consisting of silica, polymeric beads,reflective glass beads, non-reflective glass beads and mica.
 14. Thecolor proofing element of claim 12 further comprising a colorant. 15.The color proofing element of claim 14 further comprising a colorenhancing additive.
 16. The color proofing element of claim 15 whereinsaid color enhancing additive is selected from the group consisting offluorescent, pearlescent, iridescent, and metallic materials.